Automatic switch for electric heaters



M. KLETTNER AUTOMATIC SWITCH FOR ELECTRIC HEATERS Filed NOV; 14, 1924Inventor:

Patented July 13, 1926.

UNITED STATES MARTIN KLETTNER, OF DBESDEN-ALSTADT, GERMANY.

AUTOMATIC SWITCH FOR-ELECTRIC HEATERS.

Application filed. November 14, 1924, Serial No. 749,942, and in GermanyAugust 23, 1924.

The object of the present invention is an automatic switch for electricheaters. The device is intended to be used in connection with electricheaters like fiatirons, pots, rarming plates, heating cushions, warming.abinets, electric stoves, etc., and purposes to stop automatically theelectric current the moment the temperature of the heater exceeds acertain limit and to start the current again automatically as soon asthe temperature falls below a certain level, which may be higher orlower, according to the purpose of the heater. The switch to which thisinvention refers can be employed for all sorts of heaters as the contactscrews actuating the contact device are adjustable.

The use of the automatic switch effectively prevents any burning throughof the heaters. Damages caused, for example, by electric flatirons,which are left standing for a certain time, cannot happen, if thisswitch is used. The heater is always connected to the line and istherefore always ready for use without consuming too much current,because, as already mentioned, the current is automatically cut off assoon as the temperature of the'heater exceeds a previously chosen andadjusted limit. For cooking vessels, warming'plates, and heatingcushions the arrangement can be made ,so as to maintain eventemperatures below 100 C. with very slight fluctuations.

One form of the invention is illustrated in the accompanying drawing, inwhich Figure 1 is a side view of the switch with par tially openedcasing; and Fig. 2 a vertical section ab of Fig. 1.

To the plate 1, whichis made from insulating material like hard rubber,is attached a layer of asbestos 2. 3 and 3 are the terminals, which arefirmly embedded in the plate 1. On top of plate 1 is arrangedtheasbestos layer 2, to both of which the casing 4,.which also consistsof insulating material, has been secured by screws 5. The casing 4 haspartly. been removed in Fig. 1 to permit a, look into the inside of theapparatus, while it has been completely omitted in Fig. 2.

To plate 1 and an asbestos layer 2 has been attached also a laterallyU-shaped frame 6 by means of screws 7. In frame 6, by means of screws 8,a container 9 capable of cuit passes accommodating a liquid of highcubically expansive power has been arranged, and one wall 10 of thiscontainer has been executed as a membrane. 11 is, a contact screw withhead 12. The contact screw 11 is guided with its thread in a guidemember 13 secured to a spring 14, which is attached to a member 16 whichin turn is ad justable by means of the screw 15. The spring 14'carriesat its lower end the plate 17. To the member 16 is also attached atwo-legged permanent magnet 18, through the legs of which the contactscrew 11 passes freely. The magnet cooperates with the plate 17. Onplate 17, by means of a holder 19, a button 20 has been arranged, whichcauses an electric connection between the container '9 and'terminal 3*by electrically connecting the two members 21 lying between them, one ofwhich being secured to the terminal 3 and the other to the container '9.22 is a set screw, which is insulated and guided in frame 6 by placingthe insulating isc 23 between them. 24, 25, 26, 27, 28 and 29 arefastening screws for the reception of the wire connections. Screws 24and 27 on one hand and screws 25 and 26 on the other are electricallyconnected by means of the metal pieces 30 and31. From screw 26 aconnecting wire 32 leads to screw 26 and thus to terminal 3*. Anotherwire 32 leads from screw 29 to terminal 3, and finally a third wireleads from screw 27 to the set screw 22.

The method of operation is as follows: The device has the outerappearance of an ordinary two-pin wall plug and is attached to theheater in the ordinary manner by meansof the pins provided for thereception of the plug in each heaterf The current carriers areconnectedto the screws 24 and 25, respectively. In this manner one clrdirectlyfrom the screw 25 over screw 26 and the wire 32 to the terminal 3",while the other circuit passes from the screw 24 over screw 27, the setscrew 22 and the button 20 tothe terminal 3*, provided the set screw hasbeen adjusted so as to touch the button 20 withits front point. Theheater gets warm in the usual and known manner, and a part of the heatpasses over the terminals towards the container 9. The liquid keptwithin this container will now expand. If a certain maximum temperaturehas been reached, the membrane 10 is pressed outwardly far enough tocause the set screw 11 to be pressed to the right in the mannerindicated in Fig. 1. In this way the spring, contrary to the action ofthe magnet 18, is torn away with its plate 17,

from the magnet with the result that the button 20 is placed ina-certain distance from the point of the set screw 22. This causes aninterruption of current. If the heater cools off, the liquid in thecontainer 9 will contract, the membrane returns to its originalposition, and the plate 17 of the spring 14 is pulled back into itsoriginal position through spring action. The button 20 returns to itsplace at the point of set screw 22, and the connection is reestablished.In this way a certain temperature ,can be constantly maintained.

The regulation of the temperature desired, which as already mentioned,depends on the nature and purpose of the heater,

takes place by means of the screw 11 of the button '12, which is thusplaced in varying distance from the membrane, audit is therefore agreater or smaller expansion of the liquid required to cause aninterruption of current.

I claim An electric switch for electric heaters com prising a U-shapedframe, in which aclosed hollow body containing an expansible liquid, a.two-legged permanent magnet, an ad ust- "able spring contact with abutton connecting two heat conducting members are arranged, the saidspringcontact being influenced by the expansible liquid on one hand andby the permanent magnet on the other hand, while the said liquid andmagnet counteract each other, the U-sha ed frame being fitted withscrews into a p ug casing comprising a bottom-plate for the reception ofthe terminals, a covering insulating layer, connecting terminals forcurrent supply, the transmission of expansible liquid taking place overthe terminals, one connecting member, the button, theE1 other connectingmember, and the hollow bo y. o

In testimony whereof I afiix my signature MARTIN KLETTN ER.

heat from the heater to the"

